Wire plating apparatus

ABSTRACT

Wire plating apparatus includes a heating drum to which the wire to be coated is continuously passed, and from which it is passed continuously through an alkyl aluminum plating solution. From the plating solution, the wire is placed around a rinsing drum where it is rinsed with a hydrocarbon spray. The wire from the rinsing drum is then passed back around the heating drum, and back through the same path as during the previous cycle. Thus, the number of wraps around the heating drum is determinative of the number of heating, plating and rinsing cycles carried out, and these cycles are carried out automatically in the described apparatus.

United States Patent Starks et a1. 1451 Feb. 12, 1974 [54] WIRE PLATING APPARATUS 2,166,249 7/1939 Herman 1 18/69 X 2,531,561 11 1950 Eld 1.... 118 405 175] inventor-s1 Charles Starks; Larry Hmd, 2,732,319 111956 Crei j ju; ll8/6 9 x both of Ponca City Okla- 3,122,114 2/1964 Kringel et a1. 118/405 ox Assignee: Continental p y, Ponca 3,265,033 8/1966 Touze 61. al. 118/66 X City, Okla. Y

Primary ExammerMorr1s Kaplan 1 Filed! 1971 Attorney, Agent, or Firm-Ronnie D. Wilson [21] Appl. No.: 189,326

Related US. Application Data [57] ABSTRACT Wire plating apparatus includes a heating drum to which the wire to be coated is continuously passed, and from which it is passed continuously through an alkyl aluminum plating solution. From the plating solution, the wire is placed around a rinsing drum where it is rinsed with a hydrocarbon spray The wire from the rinsing drum is then passed back around the heating drum, and back through the same path as during the previous cycle. Thus, the number of wraps around the heating drum is determinative of the number of heating, plating and rinsing cycles carried out, and these cycles are carried out automatically in the described apparatus.

3 Claims, 2 Drawing Figures PA IENTEI] FEB I 2 I974 FIG.

WIRE PLATING APPARATUS This is a division, of application Ser. No. 815,690, filed Apr. l4, 1969.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to plating apparatus, and more specifically, to an apparatus for chemically plating aluminum on wire.

2. Brief Description of the Prior Art The plating or coating of steel wire with a protective material is desirable for many applications and uses of such wire. Zinc galvanization has been employed in some instances on steel plate, but is difficult to apply to wire. The zinc coatings are quite economical, and are applied by continuous hot dip galvanizing lines through which steel strip plating, or less frequently, wire is passed. Steel wire and strips are also plated with tin by an electrolytic tin plate process.

Previous to this time, there has been no economical way to apply a relatively thin, high quality film of aluminum to strip material or to wire. Were such a process available, the aluminum plated steel strip or wire would offer significant advantages over existing commercial plating processes due to the well-known desirable characteristics and chemical properties of aluminum in comparison to some of the more widely used plating materials presently employed.

It has recently been proposed to plate metal substrates with aluminum by contacting the metal with an alkyl aluminum compound at a temperature at which the alkyl aluminum compound undergoes decomposition as more fully described in US. Pat. No. 3,041,197 to Carl Berger. The primary requirement which has been identified for obtaining uniform and adherent aluminum plating on wire, particularly on steel wire, is that careful control of the temperature of the wire during the plating process is maintained. If the temperature of the wire is too high, the aluminum plating will be powdery or flaky and will not adhere to the wire. If the temperature of the wire is not sufficiently high, decomposition of the alkyl aluminum compound with which the wire is contacted in the liquid phase will not occur and plating will be unsuccessful. Moreover, in order to build up the coating or film of aluminum which is plated on steel wire when a process of contacting the hot wire with a liquid alkyl aluminum compound is carried out, the wire is repeatedly heated and then recontacted with the liquid alkyl aluminum compound. Upon such cyclical contacting of the hot wire with the alkyl aluminum compound, great care must be exercised in temperature control to prevent the occurrence of damage in the late plating cycles to the aluminum coating laid down in earlier plating cycles. This is particularly true in the case of the plating of steel wires, since, at relatively high temperatures, iron and aluminum form an intermetallic composition which adversely affects the adhesion of the aluminum to the steel.

BRIEF DESCRIPTION OF THE PRESENT INVENTION The present invention provides an apparatus for plating aluminum on wire. The method utilizing the apparatus includes the steps of initially heating the wire to within a pre-determined temperature range, then contacting the wire with an alkyl aluminum compound in the liquid phase. The wire is then removed from the 2 plating solution, reheated, then recontacted with the alkyl aluminum compound. This cyclical repetition of the heating and contacting of the solution is repeated several times, with a rinsing step being interposed between the contacting of the wire with the plating solution and the reheating steps. In the rinsing step, any excessive, undecomposed alkyl aluminum compound which remains on the wire after it leaves the plating solution is rinsed away with a hydrocarbon rinse material.

More specifically, in carrying out the steps of aluminum plating as thus broadly described, the wire is initially heated to the desired temperature by passing the wire around a heating drum which effectively heats the wire to the desired temperature. The wire is then continuously drawn from this drum into the plating solution and is further continuously drawn from the plating solution to a rinsing drum. While on the rinsing drum, the rinsing step is carried out by contacting the wire with the hydrocarbon spray solution. The wire is then returned to the heating drum and the described cycle is repeated. The steps are preferably carried out in a continuous manner with the wire being continuously passed over the heating and rinsing drums and through the plating solution which is located intermediate these drums.

An object of the invention is to provide an apparatus for continuously aluminum plating a wire.

An additional object of the invention is to provide an apparatus for continuously and automatically alternately heating and then contacting a wire with an aluminum plating solution under conditions such that an aluminum coating or plating solution under conditions such that an aluminum coating or film is built up on the wire to a desired thickness.

A further object of the invention is to provide an improved apparatus for enhancing the rate at which a high quality aluminum coating can be formed on steel wire.

Additional objects and advantages will become apparent as the following detailed description of the invention is read in conjunction with the accompanying drawing which illustrates the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic plan view of the apparatus utilized in the practice of the invention.

FIG. 2 is a vertical sectional view of the apparatus depicted in FIG. 1 taken along line 2-2 of FIG. 1.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION Referring initially to the drawings, shown therein are a heating drum 10, a plating solution vat or container 12 and a rinsing drum 14. A suitable source of electrical power 16 supplies current through electrical leads 17 to resistance elements 18 disposed inside the drum 10, and a thermocouple 20 or other suitable temperature detecting device functions in conjunction with suitable control circuitry to intermittently interrupt the current delivered to the heating elements 18 so as to maintain the heating drum 10 at a predetermined temperature.

A bank of spray nozzles 22 is disposed over the rinsing drum 14 in a position to direct the hydrocarbon rinsing liquid against the outer peripheryof the rinsing drum over its length. A wire guide structure 24 is positioned in the container 12 at a level such that at least the lowermost portion of its outer periphery is covered by a plating solution 26 located in the container. In a preferred embodiment of the invention, the drums 10 and 14 and the wire guide structure 24 are rotatably mounted cylinders having substantially parallel longitudinal axes.

A wire 28 to be plated with aluminum is extended from a reel or other source (not shown) to the heating drum 10, and is wrapped around the heating drum and extended under the guide structure 24. From beneath the guide structure 24, the wire 28 is extended to, and wrapped around, the rinsing drum 14. The wire is then passed around the heating drum 10 again, back under the guide structure 24 and again around the rinsing drum. The wire 28 is led through the described path a number of times, depending upon the thickness of the plating which it is desired to adhere thereto as hereinafter explained.

Careful temperature control must be maintained in aluminum plating wire by contact with an alkyl aluminum solution. The mechanics of the plating process involves the thermal decomposition of the alkyl aluminum compound to deposit metallic aluminum on the surface of the wire. The temperature at which such decomposition will occur varies with the type of alkyl aluminum compound in use. In general, however, the wire is heated to the extent that it will be at a temperature which is from about C to about 60C above the decomposition temperature of the particular alkyl aluminum compound in use.

The types of alkyl aluminum compounds useful in the practice of the method of the invention are those in which aluminum is bonded to one or more alkyl radicals containing from 1 to 30 carbon atoms. The valences of the aluminum which are not satisfied by alkyl radicals are satisfied by hydrogen ions. Thus, the compounds useful in the plating process have the formula AlR(R') where R is an alkyl radical containing from 1 to 30 carbon atoms, and R is selected from a group consisting of alkyl radicals containing from 1 to 30 carbon atoms and hydrogen. Aluminum diethylhydride is the preferred compound used for plating because of its relatively low decomposition temperature.

The plating solution employed is preferably a solution of one or more of the alkyl aluminum compounds and an inert petroleum distillate type solvent which boils at a temperature above the decomposition temperature of the aluminum compound, although a plating bath of pure alkyl aluminum compound has been used effectively. Most suitably, a solution containing 50 weight per cent aluminum diethylhydride in kerosine is employed.

Those skilled in the technology of alkyl aluminum chemistry will appreciate that compounds of this type are pyrophoric materials requiring adequate safety precautions in their handling to prevent fire and explosion. Accordingly, it is desirable to include in the apparatus depicted in the drawings, suitable hoods and equipment for blanketing the alkyl aluminum solution in the container 12 with an inert atmosphere.

In the process of the invention, and using the depicted apparatus, the wire 28 to be plated, which may be copper, brass. steel or other metallic materials, but which is steel in a preferred, and particularly useful embodiment of the invention, is led from a suitable source, such as a drum or spool upon which such wire is wound, to the heating drum 10. The wire is then passed around this drum in contact therewith, and is led downwardly into the plating solution 26 of the selected alkyl aluminum compound which, as has been previously indicated, is preferably aluminum diethylhydride.

The wire 28 is then passed under the wire guide structure 24 and led to the rinsing drum 14. At the rinsing drum 14, the wire is wrapped or wound around this drum and is then extended therefrom in a direction to lead back to the heating drum 10. If desired, the wire 28 may be wrapped around the rinsing drum 14 several times before being extended to the heating drum.

The wire is then extended through the same path, i.e., around the heating drum 10 with one or more wraps, under the wire guide structure 24 in the plating solution located in the container 12, and around the rinsing drum 14. In general, the number of times that the wire 28 is passed around the heating drum l0 and through the plating solution 26 will depend upon the thickness of the coating or plate which it is desired to adhere to the wire.

After the wire 28 has been wrapped around the drums 10 and 14 in the manner described and has been passed under the wire guide structure 24 intermediate the drums, the leading end of the wire is extended to a take-up device or storage reel 30 which is continuously revolved in order to draw the wire 28 continuously through the described path.

In commencing the process, the temperature of the heating drum 10 is adjusted to the value which is desired, which is in turn dependent upon the distance the heating drum is located from the plating solution 26, and upon the composition of the alkyl aluminum solution 26. As has been indicated, it is desirable that in passing around the heating drum 10, the wire 28 be heated to an extent such that at the instant it contacts the plating solution 26, it will be at a temperature of from about 5C to about 60C above the decomposition temperature of the particular alkyl aluminum compound in use. The solution of the alkyl aluminum compound located in the container 12- is preferably at a temperature of about C during the practice of the process, but a lower temperature may be employed, if desired.

As the wire 28 enters the alkyl aluminum solution 26, it is quenched or its temperature is lowered to that of the solution within a very short time interval after entering the solution. Over this time interval, however, the alkyl aluminum compound in contact with the wire 28 undergoes thermal decomposition, and metallic aluminum is deposited upon, and bonded to, the wire in a relatively uniform and defect free film or coating. The wire 28 as thus plated is then passed under the guide structure 24 which is preferably rotatably mounted to prevent the tendency of frictional contact to mar or remove a portion of the coating. The wire 28 is then passed upwardly around the rinsing drum 14 where a hydrocarbon rinsing liquid is sprayed upon the wire to remove any undecomposed alkyl aluminum compound and solvent from the wire. The effluent from the rinsing step is collected in any suitable vat or container and may be recycled to the plating solution 26 located in the container 12. The hydrocarbon rinse solution employed may be any suitable type of inert liquid material in which the alkyl aluminum solution is soluble, and with which it is non-reactive, but is preferably chemically identical with the solvent for the alkyl aluminum compound which is used in the plating solution 26.

On the first pass of the wire 28 through the alkyl aluminum plating solution 26, a relatively thin film or plating of metallic aluminum is laid down on, and bonded to, the peripheral surface of the wire. If a thicker coating is desired, the wire 28 is again passed around the heating drum where it is reheated to a temperature sufficient that the wire will be at a temperature exceeding the decomposition temperature of the alkyl aluminum compound in use at the time it re-enters the plating solution 26. The extent to which the coating or plating thickness is increased upon each pass of the wire through the plating solution 26 can be controlled by control of the extent to which the wire is preheated, which in turn determines the quenching time over which the temperature of the wire is lowered from its temperature upon entering the plating solution to the temperature of the plating solution.

It may be observed that the mechanics of temperature control of the wire 28 involves two aspects. The first of these is the control which is attainable through the employment of the resistance elements 18 and thermocouple 20 to adjust the temperature of the heating drum 10 as desired. Secondly, the degree to which the wire 28 itself is made to conform to the temperature of the heating drum 10 is in some measure controllable by selection of the number of turns made by the wire around the drum. It will be apparent also, of course, that a temperature gradient may be established over the length of the heating drum 10, so that turns of the wire made around this drum in subsequent or later passes of the wire can be accomplished at graduated temperatures calculated to afford a more precise control of the thicknesses of subsequent films or coatings built up or superimposed upon the initial film.

From the foregoing description of the invention, it will be apparent that a method and apparatus has been described which affords a relatively inexpensive technique for continuously and effectively aluminum plating wire. The apparatus is inexpensive, is mechanically simple and easily maintained, and functions to allow a fairly precise temperature control in the feeding of the wire to the plating solutionwhile permitting a maximum length of wire to be coated in a minimum time. Although a preferred embodiment of the invention has been herein described in order to enable those skilled in the art to practice the invention, it is to be understood that various changes can be effected in the described process and apparatus without departure from the basic principles of the invention. Innovations and changes of this type which continue to rely on such basic principles are therefore deemed to be circumscribed by the spirit and scope of the invention.

What is claimed is:

1. Apparatus for plating wire comprising:

a plating solution container;

guide means in said container;

a heating drum; and

a second drum, said heating drum, container and second drum being arranged in a generally triangular array so that the wire to be plated can be wrapped around the heating drum, passed through the plating solution container, passed around the second drum and back to the heating drum, and can be continuously moved through this path in a cyclical fashion; and further characterized to include means adjacent said second drum for spraying a rinsing liquid against wire wrapped at least partially around said drum.

2. Apparatus as defined in claim 1 wherein said heating drum and second drum are each rotatably mounted for rotation about the axis of the respective drum.

3. Apparatus as defined in claim 1 wherein said apparatus further comprises:

electrical heating elements inside said heating drum;

and

means for selectively controlling the current supplied to said heating elements. 

2. Apparatus as defined in claim 1 wherein said heating drum and second drum are each rotatably mounted for rotation about the axis of the respective drum.
 3. Apparatus as defined in claim 1 wherein said apparatus further comprises: electrical heating elements inside said heating drum; and means for selectively controlling the current supplied to said heating elements. 